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Phylum Nematoda

Roundworms

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Characteristics of Roundworms

• Bilaterally symmetrical body with a pseudocoelom

• 3 embryonic tissue layers

• Digestive system with separate openings for feeding and waste elimination

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• Free-living roundworms are active hunters that feed on bacteria, fungi, protists, or small invertebrates.

• Some species are parasitic that feed on plants or animals.

• Roundworms usually produce sexually.

• Nutrients absorb through the fluid in the pseudocoelom.

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Exploration of a Roundworm

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Groups of Roundworms

• Common parasitic roundworms include; pinworms, hookworms, filarial worms, and ascarids/ Ascaris .

• As many as 50% of preschool and school-age children are infected with pinworms.

• Filarial worms are a group of long, thin roundworms that live as adults in the blood or other tissues of vertebrates, including humans.

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Groups of Roundworms, continued

• Filarial worms are a group of long, thin roundworms that live as adults in the blood or other tissues of vertebrates, including humans.

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Groups of Roundworms, continued

• Ascarids are roundworms that live in the intestines of pigs, horses, and humans.

• Ascarids feed on food that passes through the intestines of their host. They can block the host’s intestines if left untreated.

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Fighting Parasites

• Human are hosts to a number of flatworm and roundworm parasites.

• A large part of the problem is that almost half of the world’s population lives in areas with inadequate sewage systems.

• In addition, about 1 billion people do not have access to clean water.

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Fighting Parasites, continued

• To prevent parasitic infections, people who live in or travel to places where parasites are common should;– wash hands frequently, – drink bottled or boiled water– eat only fully cooked meat– use insect repellent, wear protective clothing, and sleep under

netting.